1. Field of the Invention
The present invention relates to an image acquiring device and method for performing a time lapse imaging function, and more particularly to an image acquiring device and method having a time lapse imaging function capable of selecting an optimum imaging method easily.
2. Description of the Related Art
Hitherto is known an image acquiring device having a time lapse imaging function for taking and recording images automatically at specific time intervals, and, for example, an imaging device (digital still camera) disclosed in Patent Document 1 (Jpn. Pat. Appln. KOKAI Publication No. 11-112852) is known.
Such an imaging device having a time lapse imaging function is often used in a microscopic image acquiring device for taking time course changes of, for example, live cells.
The digital still camera disclosed in Patent Document 1 is designed to repeat the operation of imaging after lapse of a predetermined time interval, and imaging again after the predetermined time interval in end of the imaging.
FIG. 9 is a diagram explaining the operation of the time lapse imaging in a prior art.
In this case, the actual imaging interval Ta is the sum of an imaging interval Tb designated by an operator and an exposure time Tc.
Even if the imaging interval Ta is set by summing up the imaging interval Tb and exposure time Tc, there is no problem in general photography of extremely short exposure times ranging from ten thousandths of a second to tenths of a second.
However, in the above-described microscopic image acquiring device for taking time course changes of live cells, generally, fluorescence photography is employed.
In such a microscopic image acquiring device by fluorescence photography, since a subject of an extremely low luminance is taken, the exposure time is very long, ranging from several seconds to tens of seconds.
Therefore, when time lapse imaging as shown in FIG. 9 is applied in the microscopic image acquiring device by fluorescence photography, assuming that the sum of the imaging interval Tb designated by the operator and the exposure time Tc is set as the actual imaging interval Ta, the actual imaging interval Ta may be largely different from the imaging interval intended by the operator, and the subject may not be taken as desired by the operator.
FIG. 10 is a diagram for explaining the operation of time lapse imaging by another prior art devised to solve the above problems.
In this imaging technique, by including the exposure time Tc in the imaging interval Tb designated by the operator, imaging can be started at every predetermined time interval Tb regardless of the exposure time Tc.
However, if the exposure time Tc is intended to be included in the imaging interval Tb designated by the operator, various contradictory states may result.
FIG. 11 is a diagram for explaining an example of a contradictory state occurring in the time lapse imaging by such another prior art.
In this example, the contradiction is that the exposure time Tc determined by automatic exposure or determined manually may be longer than the imaging interval Tb set by the operator (exposure time Tc≧imaging interval Tb).
In such a contradictory state, each exposure time Tc itself is overlapped in time, and time lapse imaging is disabled.
In order to avoid such a contradiction in time lapse imaging, hitherto, by using a user interface (UI), for example, it is proposed to limit as follows:
(1) the imaging interval may not be shorter than the exposure time during setting of imaging interval, or
(2) the exposure time may not be longer than the imaging interval during setting of exposure time.
Generally, however, in time lapse imaging, the important item differs with the purpose of photography, such as photography with emphasis on the exposure time or photography with emphasis on the imaging interval, and such limitation by the UI makes it difficult for the operator to select the imaging method, or is likely to lead to operation errors.